CABLESEither JPS Superconductor+ and FX interconnects and a double run of JPS
Ultraconductor speaker cables, or Analysis Plus interconnects and Oval 12 speaker cables,
and Monarchy and various DIY AC cords.

When I got the word to review Art Audio's
Quartet mono amps, I jumped on it. First off, being of the
tube-amp-lover-persuasion, how could I pass up an opportunity like
this? Second, here was a chance to tell the world of yet another
great design from a company with a long list of great designs in
the field of tube amplifiers. I strongly feel that tube amplifiers
deliver a more natural and honest presentation of the recorded musical
event than solid-state. This leads us to reason number three: this would
give me yet another opportunity to jump on my soapbox and tell the world
that gloriously textured, harmonically correct tube bass is superior to
that of the overly tight, dry, stiff solid-state bass. OK, admittedly
that last one is more of a personal agenda, but unless there is a
serious mismatch in one's system, I challenge anyone not to have a go at
these beauties.

And beauties they are. The set under review
arrived in an all steel/chrome chassis with the optional chrome legs.
Other optional goodies include stainless steel tube surround rings for
the power tubes, glass chimneys for said power tubes, and sexy blue
illumination. If it were me, I'd go for the whole enchilada and trick it
out to the max! I did see a picture somewhere of their Carissa stereo
amp - which is identical to one mono Quartet in looks—with a beautiful
blue chassis and chrome transformer cover. This says to me that Art
Audio might be willing to custom design your very own set of Quartet
mono blocks.

The Quartets are 45/50-watt pure class-A
push-pull 845 based tubed monoblock amplifiers. The input impedance is
180 kohm, which turned out to be a great match for my Reference Line
Passive line stage. Valve Art 845 power tubes are standard issue, but
one can order them with a set of KR Audio 845s cryogenically frozen to
boot. NOS driver tubes are also an option; these came with the review
samples. The automatic biasing thing is done inside the amps just for
your convenience. The mil spec PC boards are of the hard-wired hybrid
design. There is a feedback switch on the back that allows for
adjustments from zero to 6dB. The rectifier is solid-state with
two-stage choke filters.

A word about the build quality of these
amps. Exemplary! Peeking under the bottom panel, not to mention a quick
once over of the chassis, will confirm this. From the PCs to the
hardware that is bolted on the chassis, the Quartets are built to a very
high standard. The tubes are gripped snugly by their sockets, which is
something I cannot say about either of my tube amps. The only exception
to this nicely built pair of amps is the transformer cover. Although
solidly secured to the chassis, it rings a bit when you ping on it. Not
a loud echo, but a hollow vibration nonetheless. To be fair, I have
noticed this phenomenon on other high-end, high-priced equipment. Maybe
many audio manufacturers feel a ringing cover or bonnet is not an
impediment to good sound. Although I have not contacted Art Audio about
this, it may be that they offer damping as an option. I also heard from
Dave Clark my review samples might not be representative a final
production run, which may account for any variables in chassis
manufacturing. In any case, the rest of the unit was quite solid. One
may very well hurt their fingers tapping on this pair of amps.

Before describing the music making abilities
and the sonic character of the Quartets, a few different devices were
used with these amps to bring out their best. Instillation of Hi-Fi
Tuning Silver/Gold/Ceramic fuses (courtesy of Mr. Robert Stein of Ultra
Systems) greatly enhanced the performance of these already fine amps.
After a little experimenting with these fuses, I cannot live without
them in any of my gear—that allows for an easy fuse swap. If you think
the sound of your amplifier, preamplifier, or CD player is dimensional,
clean, and liquid, wait until you install the Ultra Fuses. You ain't
heard anything yet! The second change concerned my power line
conditioner. Besides my usual Balanced Power Technologies 2.0, the very
big and beautiful Pure Power One 5.0 power conditioner was also invited
to the party. The BPTs I own are great products, but the Pure Power One
5.0 is quite a substantial piece of gear as far as cleaning up the
background and providing a "pure" and very clean platform of "power" in
which components can perform at their best. Finally, a PS Audio Digital
Link Digital to Analog converter (also in for review) was used from time
to time. For the most part—and to get a proper perspective on their
sound—the Quartets were hooked up to my regular gear with the
exception of the Hi Fi tuning fuses which I simply could not take out.

There seems to be two kinds of kids in the
world. There are the ones who rip the boxes that their new toys come in
into pieces as fast as they can in getting to the toys inside so they
can start playing. Then there are the kids who methodically open the box
without damaging it while carefully taking out the toy and glancing at
the instructions all at the same time. The playing comes in its own
time. The latter become audiophiles, in that the Quartets induced the
behavior in kids of the former variety. I did not rip the boxes apart to
get the amps out, though I did pull these quite substantial beauties out
and set them up as fast as possible. In fact, these amps are pretty easy
to set up. To be honest, I had so much fun listening to these amps from
the get go that it was hard to get serious about taking notes and do any
kind of critical listening. But as several of the gentleman said in the
movie Man on Fire, "I am a professional", so onward and upward!

I started out listening to the Pat Metheny
Group and Little Milton CDs. Track one of the soundtrack to the
Falcon and the Snowman by the PMG starts out with the Ambrosian
Choir singing Psalm 21 and melds into Flight of the Falcon.
I give this recording a 3½ stars out of 5 even though names like Bob Clearmountain, Bob Ludwig, Abby Road Studios, and Masterdisk are
plastered all over the back cover. Actually, you need a magnifying glass
to read the back of the CD. The Ambrosian Choir conducted by John McCarthy sounded spacious, reverberant, and clear. The small details and
micro dynamics that the various percussion instruments created on songs,
such as track 6, "Extent of the Lie" and track 7, "The Level of
Deception" were both clear and distinct. I heard no smearing. Each sound
was clearly resolved in space, but never sounded thin or bright. These
sounds had an appropriate holographic dimension to them, along with the
proper timbre of each instrument.

Similarly, on the Little Milton CD, For
Real, vocals throughout this disk had a natural solidity to them. By
this, I mean vocals were coming from the midrange as solidly as the bass
was and up through the top end. The vocals, as heard on the PMG disk,
had the same level of dimension and natural timbre. I am sure I have
mentioned it before, but the standout tracks on this disk are "A Rainy
Night in Georgia" and his great cover of that Bee Gee's tune, "To Love
Somebody". Milton makes it one of his own and it really showcases the
vocals of this great musician who sadly recently left us. Although
Milton strays slightly from the blues on these two tracks, he does so
with grace and class while putting his own unique spin to these classic
tunes.

Time for more favorites and on went Ginger
Bakers, Going Back Home CD. On track 10, "East Timor", Baker's
vocals were more fleshed out with the accompanying instruments - in this
case drums, guitar, and bass courtesy of Baker, Bill Frisell, and
Charlie Hayden. This all sounded more natural, dimensional, and solid
than when played through my usual amps. It was the solid focus,
precision, and clarity along, with a harmonic rightness, that kept
coming back to impress disc after disc - whether it be CD or vinyl. It
was Baker slightly left and to the back of Frisell, and it was Hayden
slightly to the back and right of Frisell. There it was: a solid
soundstage, rock solid images and tone, texture and harmonics that drew
one into the performance no matter the quality of recording.

At first
listen—compared to both of my own tube amps, which sound richer in the
bass than do the Quartets—the lowest bass on these amps sounded
slightly leaner. The difference between them is that the Quartets
differentiate the bass notes and texture of instruments like the
thoroughbreds that they are. The bass never sounds chopped up or
sectionalized. The bass and drum on tracks 2 and 10, again on Baker's
Going Back Home, had fuller and thicker sound through the Margules
and Antique Sound Labs. But with the Quartets, both bass and drums
sounded more distinct in not only the color of each instrument, but also
in how it unraveled the musical lines and bass notes. Yet at the same
time, the Quartets sounded solid, very coherent, and powerful. As it
turned out, the bass also went deeper and with greater impact than heard
on either of my reference amps. What Art Audio has wrought from these
845 power tubes, in the bass and just above this region, is very taut
and solid. Way better than that of similar designs using the same tube.
The solidity, clarity, and focus again paying big dividends.

Although my Kuzma Stabi S turntable was
pressed into service quite a bit, it was the digital rig that got the
workout. A recent purchase is a double CD by pianist, Lang Lang, called
Memory. This CD features works that evoke his "childhood
pianistic explorations". Works from such artists as Mozart, Chopin, and
Schumann. Boy, what evokes my childhood memories of any kind was cartoon
music. But then again I am sure a good bit of cartoon music is well
grounded in the classics. Besides Lang Lang's technical artistry and
love for this music, the Quartets also contributed in a very positive
way with the proceedings. The low-level resolution and the low noise
floor of these amps was very impressive. Similarly on Yarlung Records CD
release, The Piano, Evening Conversations featuring David Fung
playing solo piano. Here the Quartet amps did a fine job of showing the
intimate scale of the piano on works by Mozart, Chopin, and Schumann,
among others.

Similarly the larger setting of the Janaki
String Trio, also on Yarlung Records, seemed to breathe as this fine
group of musicians went from soft to loud and from solo to the full trio
on the more dramatic passages. I find track 11, Lefkowitz' "Duet for Violin and
Viola" quite an interesting piece of music. These recordings, especially
the Yarlung's, are recorded quite well and the playing is magnificent.
The Quartets reproduced the voicing of these "wooden" instruments' quite
naturally. The sound was neither too cool, nor too warm with a tonal
pallet spread out like a male peacock at mating time. And as always
throughout this audition, the Quartet did it very cleanly.

Just for fun I thought it would be
interesting to compare the Quartets to both my Margules U280 SC and the
less expensive, but highly modified, Antique Sound Labs MGSPM25DT mono
blocks. The Margules is a sweet and clean all-tube amp with many
user-friendly features. It fared better in its 30-watt triode mode than
in its 60-watt ultra linear setting in sounding cleaner overall without
the need to be pumping out more watts. Its soundstaging is very good,
but noticeably smaller than either of the other mono blocks. Even so,
the Margules U280 SC sounded slightly more organic and warmer than the
Quartets. Although details were not lacking, they were not as easily
fleshed out as heard from the big Art Audio amps. Still the Margules'
many strengths has made it my reference amp for over three years and
counting.

Boy, have I had fun with my ASL mono blocks.
They get used quite a bit and they are fun, fun, fun! They do not have
the greatest razor sharp resolution or gargantuan bass slam, but their
very wide and deep soundstage and stable imaging, along with very nice
harmonic and tone reproduction, make them very listenable over long
periods. They also respond very well to tweaks and tube rolling. Right
now a quartet of Electro Harmonic KT-90 power tubes and a pair of J&J
12AX7s are divided up equally in each amp serving their purpose quite
well. Yes, they are warmish and might not knock you over with rock-solid
dynamics, but there is enough detail, bass, and musicality for me to
keep them around for many a year—they get the heck played out of
them...

Okay, so the Art Audio Quartets seem to be
waiting on sidelines and polishing their fingers, just itching for me to
finish up the comparison and say, "Adios boys"! Yes the music was more
easily fleshed out, and the soundstage and instruments more focused and
anchored in space. Yes, there were more natural and realistic timbres,
and more solid and textured bass. And yes, they sounded cleaner and more
effortless with a more real with a beautiful decay and dimensional ease.
And yes again, more money should bring to your audio table not only
better build quality and aesthetics, but also an effortless
ability to convey the music. Although expensive—I have railed at that
aspect of the high-end many times before—just looking, touching, and
listening to the Quartets makes you know that they are worth every
penny. What Art Audio has done in the design of these amps is to employ
the harmonic presentation of tubes, along with the transparency,
dynamics, and frequency range of solid-state amplification in one
beautiful package. I am in love. Francisco Duran